The present invention relates to closing supple sleeves by sealing in order to enclose and to isolate certain objects, together with holding tongs for the sleeve, which facilitate the process. The domain of the invention is more precisely that of leak-proof chambers under controlled pressure lower than atmospheric pressure such as glove boxes, from where it is sometimes necessary to extract parcels, taken out through openings around which flexible vinyl sleeves have been set in place. Afterwards, heating tongs are brought close to a position near the sleeve between the objects and the link with the opening to the chamber, in order to carry out three seals in this place before selecting one. The objects can then be taken away without polluting externally, and in the same way the portion of the sleeve remaining fixed to the chamber comprises no opening which could compromise its seal.
Despite its simplicity, this process is fastidious in practice. The low pressure chamber tends, in general, to cause pleats in the sleeves, to suck them in and to deform them continually.
If the sleeve is sealed when a pleat has been formed, the work risks being incorrect and the seal incomplete along its length. If there is tension on the sleeve during sealing, there is a possible risk of confinement rupture at this point, which is unacceptable. Therefore one has to take care while working, and a second operator is used in practice just to support the parcel and to hold the sleeve while his or her colleague is engaged in sealing.
The present invention proposes an improvement of this process, and the original means used for carrying it out comprise supplementary tongs, whose function is not to seal but to prevent the formation of pleats by holding the sleeve flat over its whole width, to allow continuous aspiration between the parcel and the chamber during the preparation and to avoid tension in the sleeve during sealing by setting the holding tongs against the link with the opening because of the low pressure in the chamber.
These tongs comprise two articulated branches provided with facing edges able to be set apart to a distance close to the thickness of the sleeve when they are set parallel in a closure position of the branches; in addition, indentations are grooved in one of the facing edges.
The tongs are set in place before the operation of sealing the sleeve, by setting them on a portion of the sleeve at the level of the opening of the chamber.